JP2009207812A - Radiation image capturing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide high-quality images usable for diagnosis or the like while reducing motion artifact when sequentially capturing the same subject a plurality of times. <P>SOLUTION: When imaging the chest of a subject 18, a control section 24 defines an image acquired at a second imaging as a diagnosis image, determines that an image quality correction process in the first imaging is "not required", greatly reduces an imaging time interval relative to that at other imaged sites to reduce the motion artifact of an energy subtraction image, and determines that the image correction process in the second imaging is "required" so as to provide the high-quality diagnosis image. When the imaged site is a site other than the chest (for example, the lumbar or the like), the degree of the imaging time interval affecting on the motion artifact is small, so that the control section 24 defines the image captured at the first imaging as the diagnosis image, determines that the image correction process in the first imaging is "required", and the imaging time interval is set greatly larger than that at the other imaged sites so as to provide the high-quality diagnosis image. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a radiographic image capturing apparatus, and more particularly, to a radiographic image capturing apparatus having a function of detecting radiation transmitted through a subject as an image and capturing the same subject multiple times in succession.

  In radiographic image capturing, the same part of the subject is imaged with different tube voltages, and the image obtained by imaging with each tube voltage is weighted and the difference is calculated to calculate the bones in the image. There is known a technique for obtaining an image (energy subtraction image) in which one of an image portion corresponding to a hard tissue and an image portion corresponding to a soft tissue is emphasized and the other is removed.

  As a method for generating an energy subtraction image, a stimulable illuminant is used for the X-ray detector, and a filter such as a copper plate is inserted between the two detectors to substantially change the tube voltage by one imaging. Conventionally, a technique for obtaining two images and generating an energy subtraction image from these images is known.

  On the other hand, an X-ray imaging system using a semiconductor detector is used, X-ray continuous shooting is possible in a short time, and an energy subtraction image is generated using images taken twice in succession. It has become. However, in the semiconductor detector, image information in the first shooting may remain in the detector (hereinafter referred to as an afterimage) and may affect the image in the second shooting due to the photoconductive effect. In Patent Document 1, the first imaging is performed at a low dose and the second imaging is performed at a high dose out of two consecutive imaging, so that the imaging can be performed twice while taking into consideration the influence of the photoconductive effect. A technique for reducing the time interval is disclosed.

  Patent Document 2 discloses that, among two consecutive imaging operations, the first imaging is performed at a low dose and the image is read out in a high-speed / low-definition mode. A technique is disclosed in which an image is read in a high-definition mode so that the time interval between two imaging operations is reduced to reduce the influence (motion artifact) of body movement of the subject.

  In Patent Document 3, the first imaging is performed at a low dose to acquire the first image data set, the gain is decreased and the pixel acquisition resolution is increased, and then the second imaging is performed at a high dose. A configuration is disclosed in which a second image data set is acquired and first and second offset images are acquired.

Further, as a technique related to the above, Patent Document 4 discloses that a patient's cardiac cycle is monitored to find a first heartbeat trigger, and the patient is imaged with a first X-ray energy in accordance with the first heartbeat trigger. Forming a first X-ray image, monitoring the patient's cardiac cycle to find a second heartbeat trigger, and taking a second X-ray energy in response to the second heartbeat trigger, A technique for forming two X-ray images is disclosed.
JP 2002-243860 A Japanese Patent Laid-Open No. 2004-261489 JP 2003-284710 A JP 2002-325756 A

  The techniques described in Patent Documents 1 to 4 are all techniques for reducing motion artifacts in energy subtraction images. In particular, the techniques described in Patent Documents 1 to 4 reduce the shooting time interval in a plurality of shootings as much as possible. Although motion artifacts are reduced, the image obtained by performing multiple shootings to generate an energy subtraction image is not limited to the generation of an energy subtraction image, but also used for diagnosis, etc. There is also a need. However, images that can be used for diagnosis and the like are required to have high image quality, whereas reducing the shooting time interval reduces image quality as in the high-speed / low-definition mode described in Patent Document 2. They are connected and conflicting.

  The present invention has been made in consideration of the above facts, and when photographing the same subject several times in succession, it is possible to obtain a high-quality image that can be used for diagnosis or the like while reducing motion artifacts. It is an object to obtain a radiological imaging apparatus.

  In order to achieve the above object, a radiographic imaging apparatus according to the first aspect of the present invention includes a radiation generation unit that generates radiation, and an image detection unit that detects the radiation generated by the radiation generation unit and transmitted through the subject as an image. And a control means for changing a photographing time interval in the plurality of photographings according to a set photographing part of the subject when photographing the same subject a plurality of times continuously. .

  When photographing the same subject a plurality of times in succession, it is desirable that the photographing time interval be as short as possible in consideration of reduction of motion artifacts. However, motion artifacts are a major problem when photographing the chest, etc., where the organs such as the heart that work with involuntary muscles fall within the imaging range, while the imaging time interval is somewhat longer when imaging with the area moving by voluntary muscles. However, motion artifacts can be suppressed by other means (for example, holding the imaging part from the outside or requesting the subject not to move the imaging part), and the imaging time interval affects the motion artifact. The degree of influence varies depending on the imaging region of the subject. In addition, afterimages become more prominent as the radiation dose at the time of imaging increases, and if the imaging time interval is short, it affects the next imaging, so the imaging time interval becomes longer as the radiation dose at the time of imaging increases. However, the optimum value of the radiation dose at the time of imaging varies depending on the imaging region of the subject. Also, when taking multiple shots with different radiation doses to obtain an energy subtraction image, either an image at a low tube voltage or an image at a high tube voltage is suitable for use in diagnosis or the like. Whether or not there is a difference depending on the imaging region of the subject. Furthermore, when imaging is performed a plurality of times with different tube voltages, it is difficult to reduce the tube voltage in a short time as control for the radiation generating means, so it is desirable to perform imaging with a low tube voltage → a high tube voltage.

  As described above, the reduction of motion artifacts and the image quality are related to the imaging time interval. However, the degree of the influence of the imaging time interval on the motion artifact and the radiation dose in imaging that can be used for diagnosis, etc. The tube voltage differs depending on the imaging region of the subject. Based on the above, in the first aspect of the present invention, when the same subject is continuously photographed a plurality of times, the photographing time interval in the plurality of times of photographing is changed according to the set photographing region of the subject.

  As a result, for example, for an imaging region where the influence of the imaging time interval on the motion artifact is large, the motion artifact is reduced by shortening the imaging time interval, and the radiation dose in imaging of an image that can be used for diagnosis or the like is reduced. For a relatively large imaging region, it is possible to improve the image quality by increasing the imaging time interval. Therefore, according to the first aspect of the present invention, it is possible to obtain a high-quality image that can be used for diagnosis or the like while reducing motion artifacts when the same subject is continuously photographed a plurality of times.

  In the first aspect of the present invention, when the same subject is photographed a plurality of times consecutively, for example, as described in claim 2, the control means is configured to perform each time regardless of the set photographing region of the subject. It is preferable that the radiation generating means is controlled so that the dose in the imaging of the image increases monotonously. As described above, in consideration of the effects of afterimages, it is necessary to increase the imaging time interval as the radiation dose during imaging increases. On the other hand, in the invention described in claim 2, since the radiation generating means is controlled so that the dose in each imaging increases monotonously, the imaging with the maximum radiation dose is performed in the nth imaging. Thus, the motion artifact can be reduced by reducing the average value of the n-1 photographing time intervals.

  In the first aspect of the invention, since it is difficult to control the tube voltage from a high tube voltage to a low tube voltage in a short time, the control means, for example, as described in claim 3, In the case of imaging a plurality of times continuously, it is preferable that the radiation generating means is controlled so that the tube voltage of the radiation in each imaging is monotonously increased regardless of the set imaging region of the subject. Thereby, the motion artifact can be reduced by reducing the average value of the n-1 photographing time intervals.

  Further, in the invention described in claim 3, the control means outputs the image obtained by the first imaging as a diagnostic image, for example, as described in claim 4, or is obtained by the second imaging. It is preferable to switch whether to output an image as a diagnostic image according to the set imaging region of the subject.

  Of multiple images obtained by multiple imaging, images with higher tube voltage are suitable for diagnosis in the chest, etc., and images with low tube voltage are suitable for diagnosis in regions such as the lumbar spine and limb bones ing. According to the fourth aspect of the present invention, an image suitable for diagnosis can be used according to the imaging region.

  Further, in the first aspect of the invention, changing the photographing time interval in a plurality of photographings according to the set photographing part of the subject, for example, photographing in a plurality of photographings as described in claim 5 Storage means for storing the set value of the time interval for each imaging part of the subject is provided, and the control means reads out the setting value of the imaging time interval corresponding to the set imaging part of the subject from the storage means, and controls the imaging time interval It is realizable by comprising so that it may be used for.

  Further, in the invention according to claim 5, the control means sets the shooting time interval read from the storage means when the change of the shooting time interval is instructed via the instruction means as described in claim 6, for example. It is preferable that the setting value is changed according to the instruction, and the changed setting value is used for controlling the photographing time interval. This adjusts the imaging time interval so that motion artifacts are further reduced, such as measuring the cardiac cycle of the subject (subject) and changing the imaging time interval to approach the measured cardiac cycle. It is also possible to do.

  Further, in the invention described in claim 5, as described in claim 7, for example, the storage means also stores parameters for defining imaging conditions in each imaging among a plurality of imagings for each imaging region of the subject. In addition, the control unit may be configured to read out the parameter corresponding to the set imaging region of the subject from the storage unit and use it for controlling the imaging condition in each imaging among a plurality of imagings. Note that the above imaging conditions include, for example, at least one of tube voltage, tube current, radiation generation time, and distance to the subject in the radiation generation means.

  In the seventh aspect of the invention, as described in the eighth aspect of the invention, for example, the control means is instructed to change the photographing condition in a specific number of times of photographing through the instruction means. In this case, the shooting conditions in the specific shooting specified by the parameter read from the storage means are changed, and the shooting conditions in the shooting other than the specific times out of the multiple shootings are also set in the specific shooting. It is preferable to change according to the imaging conditions after the change in. In radiographic image capturing, for example, it is necessary to change the imaging conditions depending on the physique of the subject (subject). However, in the invention according to claim 8, the imaging conditions in a specific time of imaging are specified via the instruction means. When the change is instructed, the shooting conditions for shooting other than a specific number of times are changed in conjunction with each other, so that the shooting conditions for each time of shooting in a plurality of times of shooting can be easily changed.

  In addition, in the generation of energy subtraction images, considering that the difference in tube voltage at the time of shooting a plurality of images used for generation of energy subtraction images gives a higher-contrast energy subtraction image with appropriate image quality, In the invention described in item 8, when the tube voltage in the radiation generating unit is included in the imaging conditions, the control unit changes each time when the tube voltage is changed at a specific time as described in claim 9, for example. The tube voltage in the photographing other than a specific time may be changed so that the difference in tube voltage in the photographing is not smaller than the difference in tube voltage defined by the parameter read from the storage means. preferable.

  As a result, even when an instruction to change the tube voltage in a specific number of times of shooting is instructed, the generation of the energy subtraction image does not deteriorate the image quality of the generated energy subtraction image. The tube voltage in shootings other than the times is changed in conjunction, and it is possible to prevent the deterioration of the image quality of the energy subtraction image when the change of the tube voltage in specific shootings is instructed. .

  According to the first aspect of the present invention, the acquisition / correction processing is performed to improve the image quality of the acquired image while acquiring the image detected by the image detection unit from the image detection unit during each shooting. When the correction unit is provided, the control unit switches whether to perform the image quality correction processing by the acquisition / correction unit according to the set imaging region of the subject, for example, as described in claim 10. It is preferable to configure as described above. When the above acquisition / correction means performs image quality correction processing, the acquired image is improved in image quality, while it takes time to acquire an image from the image detection means, so the shooting time interval until the next shooting is prolonged. Therefore, depending on the photographing part of the subject, the image quality of the energy subtraction image is deteriorated due to the motion artifact.

  On the other hand, in the invention according to the tenth aspect, whether or not to perform the image quality correction processing by the acquisition / correction means is switched according to the imaging region of the subject, and therefore, for example, the degree of influence of the imaging time interval on the motion artifact is For large imaging sites, when taking images that are not used for diagnosis, etc., the image quality correction processing by the acquisition / correction means is not performed and the imaging time interval is shortened to reduce motion artifacts. For imaging parts with relatively large radiation doses in possible imaging, at least when imaging images used for diagnosis, etc., image quality correction processing by the acquisition / correction means is performed by increasing the imaging time interval and performing high image quality It is possible to optimize the image quality correction processing according to the subject's imaging region. Can.

  According to the first aspect of the present invention, an image quality correction process for improving the image quality of an acquired image is performed while acquiring an image detected by the image detection unit from the image detection unit during each shooting. When the acquisition / correction unit is provided, the control unit determines whether to perform the image quality correction processing by the acquisition / correction unit, for example, as described in claim 11. It is preferable to configure to switch the photographing as a unit. This makes it possible to set or switch whether or not the image quality correction processing is performed by the acquisition / correction means for each captured image. Emphasis is placed on the shooting interval when shooting frame-by-frame video (semi-video). It is possible to perform shooting that focuses on image quality, or to focus on image quality.

  Further, in the invention according to claim 10 or claim 11, the image detection means holds the switching means that is turned on / off in response to the on / off signal supplied via the first signal wiring and the signal charge according to the irradiation radiation dose. In the configuration in which a plurality of pixel units each including a holding unit are provided, image quality correction processing by the acquisition / correction unit includes, for example, a signal output from the second signal wiring as described in claim 12 Is obtained for each time when the switching means is on and off, and leakage noise correction processing that subtracts the output signal at the time of off from the output signal at the time of on-off, and the conversion of the output signal to digital data is performed multiple times and averaged Suppression processing can be applied.

  As described above, in the present invention, when the same subject is shot a plurality of times continuously, the shooting time interval in a plurality of shootings is changed according to the set shooting region of the subject. When the same subject is continuously photographed a plurality of times, it has an excellent effect that a high-quality image that can be used for diagnosis or the like can be obtained while reducing motion artifacts.

  Hereinafter, an example of an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a radiographic image capturing system 10 according to the present embodiment. The radiographic imaging system 10 includes a radiation generation unit 12 that generates radiation (for example, X-rays (X-rays) and the like), a radiation detection panel 14 that is spaced apart from the radiation generation unit 12, a microcomputer, and various electric devices. A control device 16 configured to include a circuit and acquire image information from the radiation detection panel 14 and perform various processes is provided. Between the radiation generation unit 12 and the radiation detection panel 14 is an imaging position where the subject 18 is positioned at the time of imaging, and carries image information by passing through the subject 18 emitted from the radiation generation unit 12 and positioned at the imaging position. The irradiated radiation is applied to the radiation detection panel 14.

  The radiographic image capturing system 10 according to the present embodiment corresponds to the radiographic image capturing apparatus according to the present invention, the radiation generating unit 12 is a radiation generating unit according to the present invention, and the radiation detection panel 14 is according to the present invention. In addition to the image detection means (specifically, the image detection means according to claim 12), the control unit 24 (described later) of the control device 16 is a control means according to the present invention (specifically, the control means according to claims 2 to 10). ) Respectively.

  The control device 16 includes a radiation generation control unit 20, a signal detection correction unit 22, a control unit 24, a display 26 capable of displaying an image and the like, and an operation panel 28 including an input device such as a keyboard and a pointing device such as a mouse. ing. The radiation generation control unit 20 is connected to the radiation generation unit 12 and the control unit 24, and controls the tube voltage, tube current, and radiation generation time when the radiation generation unit 12 generates radiation according to an instruction from the control unit 24. As a result, the dose of radiation generated by the radiation generator 12 is controlled. Although details of the signal detection correction unit 22 will be described later, every time the subject 18 is photographed, the image signal is read from the radiation detection panel 14 and converted into digital image data, and the image data obtained by the conversion is also read. Are subjected to image quality correction processing (details will be described later) such as leakage correction processing and electrical noise suppression processing.

  The control unit 24 is composed of a microcomputer or the like, and controls the photographing of the subject 18 in accordance with an instruction input via the operation panel 28 or uses the image data input from the signal detection correction unit 22 to generate an energy subtraction image. Image processing such as generation is performed, and processing for providing a predetermined user I / F via the display 26 and the operation panel 28 is performed. The control unit 24 includes a non-volatile storage unit 24A including an HDD (Hard Disk Drive), a flash memory, and the like, and an imaging condition information DB (database) is stored in the storage unit 24A. The contents of the shooting condition information DB will be described later. The storage unit 24A also stores a program for the control unit 24 to perform a continuous shooting process described later.

  The radiographic image capturing system 10 includes an imaging region moving unit 30. The imaging part moving unit 30 includes an actuator or the like that can move the radiation generating unit 12 and the radiation detection panel 14, and a part to be imaged in the subject 18 (imaging part: chest, lumbar spine, limb bone, breast, etc.). When notified from the control device 16, the radiation generation unit 12 and the radiation detection panel 14 are moved to a position for imaging the notified imaging region of the subject 18. Note that the positions of the radiation generation unit 12 and the radiation detection panel 14 for imaging a certain imaging region of the subject 18 also differ depending on the physique of the subject 18, and therefore the imaging region moving unit 30 includes the operation panel 28. When the adjustment of the imaging position is instructed via the button, the positions of the radiation generation unit 12 and the radiation detection panel 14 are adjusted in accordance with the instruction.

  Next, the configuration of the radiation detection panel 14 and the signal detection correction unit 22 will be described. In the radiation detection panel 14, a photoelectric conversion layer (not shown) that absorbs radiation and changes into a charge is formed on the TFT active matrix substrate 34 shown in FIG. 2, and a bias connected to a high-voltage power source is further formed thereon. An electrode (not shown) is formed and configured. The photoelectric conversion layer is made of amorphous a-Se (amorphous selenium) containing, for example, selenium as a main component (for example, a content rate of 50% or more), and when irradiated with radiation, the amount of charge corresponding to the amount of irradiated radiation. The generated radiation (electron-hole pair) is internally generated to convert the irradiated radiation into charges. Thereby, the image information carried by the irradiated radiation is converted into charge information.

  In addition, on the TFT active matrix substrate 34, a pixel unit 40 including a storage capacitor 36 for storing charges generated in the photoelectric conversion layer and a TFT 38 for reading out the charges stored in the storage capacitor 36 (note that FIG. 2, a plurality of bias electrodes and photoelectric conversion layers corresponding to the individual pixel units 40 are schematically shown as photoelectric conversion units 42), and are arranged in a matrix, and further along the direction of arrow A in FIG. And a plurality of gate wirings 44 for turning on and off the TFTs 38 of the individual pixel portions 40 and accumulation through the TFTs 38 that are extended and turned on in the direction of the arrow B perpendicular to the direction of the arrow A in FIG. A plurality of data wirings 46 for reading accumulated charges from the capacitor 36 are also provided.

  On the other hand, the signal detection correction unit 22 includes a gate line driver 48 connected to each gate wiring 44 of the radiation detection panel 14. The gate line driver 48 is connected to the gate wiring 44 that has supplied the ON signal by supplying a high-level voltage signal (ON signal) to the specific gate wiring 44 when the signal charge is read from the radiation detection panel 14. The TFT 38 of each pixel unit 40 is changed from OFF to ON, and after a certain time, the supply of the ON signal to the gate wiring 44 is stopped, so that the gate wiring 44 that has supplied the ON signal is connected. A gate line driving process for changing the TFT 38 of each pixel unit 40 from on to off is sequentially performed on the individual gate wirings 44.

  The signal detection / correction unit 22 includes the same number of operational amplifiers 50 as the number of data wirings 46 provided on the TFT active matrix substrate 34, and the individual data wirings 46 of the radiation detection panel 14 are inverted inputs of the operational amplifiers 50 different from each other. Each end is connected. Each operational amplifier 50 has a non-inverting input terminal connected to a GND wiring (ground wiring), one end of a capacitor 52 connected to the inverting input terminal, and the other end connected to an output terminal. . With the above configuration, each operational amplifier 50 and capacitor 52 functions as a charge amplifier that integrates a current (signal charge) flowing through the data wiring 46 connected to the inverting input terminal and outputs a signal having a level corresponding to the integration result. .

  The output terminal of each operational amplifier 50 (charge amplifier) is connected to one of a plurality of input terminals of a multiplexer (MUX) 54 via an amplifier and sample hold circuit (not shown), and the output of each charge amplifier. The signal is input to the MUX 54 in parallel. The output terminal of the MUX 54 is connected to the input terminal of the A / D converter 56, and the MUX 54 selects a plurality of input terminals in order, and the signal input via the selected input terminal is the A / D converter 56. Output to. As a result, parallel-serial conversion and A / D conversion (analog-digital conversion) are sequentially performed on a plurality of signals (the same number as the number of data wirings 46) input in parallel to the MUX 54.

  The output end of the A / D converter 56 is connected to the input end of the image quality correction processing unit 58, and the output end of the image quality correction processing unit 58 is connected to the input end of the control unit 24 (see FIG. 1). The image quality correction processing unit 58 performs leak correction processing and electrical noise suppression processing as image quality correction processing for improving the image quality of the image, and then outputs data (image data) after the image quality correction processing to the control unit 24.

  In the radiation detection panel 14 according to the present embodiment, in order to protect the TFT 38 when a large dose of radiation is irradiated, the charges accumulated in the storage capacitors 36 of the individual pixel units 40 by irradiation with the radiation are used. A configuration in which the leakage current is positively supplied to the data wiring 46 is employed. For this reason, only the leakage current flows through the data wiring 46 during the period when the gate line driver 48 does not supply the ON signal to any gate wiring 44, and the gate line driver 48 transmits the ON signal to any gate wiring 44. During the supply period, a current in which a leakage current is superimposed on a current corresponding to the signal charge stored in the storage capacitor 36 flows through the data wiring 46. In addition, the leak current flowing through the data line 46 is attenuated with time and becomes zero. For this reason, when the result of integrating the current flowing through the data wiring 46 by the charge amplifier is used as an image as it is, a strip-like image quality defect (artifact) extending in the vertical direction from the large dose irradiation region in the image occurs (this phenomenon is tailed). Also called pull).

  For this reason, the image quality correction processing unit 58 performs the integration of the current (signal charge) flowing through the data wiring 46 with respect to the charge amplifier in the ON period in which the TFT 38 is ON and the TFT 38 is ON for each gate wiring 44. Leak correction is performed to correct the influence of the leakage current by subtracting the off period data from the on period data. Note that the process of simply subtracting off-period data from on-period data as described above increases electrical noise by a factor of √2 and causes white-out image quality defects (artifacts) in part of the image. Since there is a harmful effect, the moving average value of the data in the off period (for example, the moving average value in the range of several pixels in the main scanning direction (the direction of the gate wiring 44) and the sub scanning direction (the direction of the data wiring 46)) is calculated. The moving average value of the data during the off period may be subtracted from the data during the on period.

  Further, the image quality correction processing unit 58 inputs the same analog signal to the A / D converter 56 a plurality of times to perform A / D conversion for the same analog signal a plurality of times, and obtained by each A / D conversion. Electrical noise suppression processing is performed to output the average value of the digital data as image data. By this electric noise suppression processing, random noise added to the digital data during A / D conversion by the A / D converter 56 is suppressed.

  However, when the image quality correction processing unit 58 performs the previous leak correction processing, the image is read from the radiation detection panel 14 to the control unit 24 after starting reading of the image as compared with the case where the leak correction processing is not performed. When the required time (readout correction time) until data is output is doubled and the image quality correction processing unit 58 performs the electrical noise suppression process for performing A / D conversion four times, the electrical noise suppression process is performed. Compared to the case where there is no read correction time, the read correction time is four times longer. For this reason, the image quality correction processing unit 58 according to the present embodiment can switch whether or not to perform the leak correction processing and the electric noise suppression processing, and only when the execution is instructed from the control unit 24. Processing and electrical noise suppression processing are performed. The signal detection correction unit 22 including the image quality correction processing unit 58 corresponds to the acquisition / correction unit described in claim 10 (specifically, claim 12).

  Next, the operation of this embodiment will be described. In the present embodiment, the imaging condition information DB stored in the storage unit 24A of the control unit 24 includes a plurality of times (for example, twice) for generating an energy subtraction image as shown in the following Table 1 as an example. The radiographic imaging system 10 captures information such as the imaging time interval in each imaging, the tube voltage of the radiation generator 12 in each imaging, the presence or absence of image quality correction processing, and which times an image is output as a diagnostic image. It is stored in advance for each imaging part of the possible subject 18.

In Table 1, “diagnostic image” “first time” indicates that the image obtained by the first imaging is output, and “second time” indicates that the image obtained by the second imaging is output as the diagnostic image. I mean. Thus, the storage unit 24A corresponds to the storage unit described in claim 5 (specifically, claim 7).

  Next, with reference to FIG. 3, continuous shooting processing performed by the control unit 24 when the user operates the operation panel 28 to instruct a plurality of times of shooting for generating an energy subtraction image. I will explain.

  In this continuous photographing process, first, in step 100, a photographing condition setting screen as shown in FIG. As shown in FIG. 4, the imaging condition setting screen according to the present embodiment includes a setting / display field 70 for setting and displaying an imaging region, and display of the tube voltage of the radiation generating unit 12 in the first imaging. And a setting / display field 72 for performing change setting, a setting / display field 74 for displaying and changing the imaging time interval, and a display / change setting for the tube voltage of the radiation generator 12 in the second imaging. A setting / display field 76 for performing an operation and a button 78 for instructing start of imaging are provided, respectively, and a message requesting selection of an imaging region, change of imaging conditions when necessary, and an instruction of “imaging” 80 is displayed and configured. When the shooting condition setting screen is displayed on the display 26, the setting / display fields 70 to 78 are all blank.

  In the next step 102, it is determined whether or not an imaging region has been set by the user, and step 102 is repeated until the determination is affirmed. When the user confirms the imaging condition setting screen displayed on the display 26 and refers to the message 80 displayed in this screen and recognizes that the imaging region needs to be set, imaging will be performed from now on. An operation for setting an imaging region to be performed in the setting / display field 70 is performed via the operation panel 28. When the operation is performed by the user, the determination in step 102 is affirmed and the process proceeds to step 104, the imaging part set in the setting / display field 70 by the user is recognized, and the imaging part moving unit 30 recognizes it. The radiation generation unit 12 and the radiation detection panel 14 are moved to a position where the imaged region can be imaged.

  In step 106, the imaging condition information corresponding to the imaging part recognized in step 104 (imaging part set by the user) is read from the imaging condition information DB into the memory, and the first imaging is read out of the read imaging condition information. The tube voltage of the radiation generating unit 12 at the time is displayed in the setting / display field 72 in the screen, the imaging time interval is displayed in the setting / display field 74 in the screen, and the tube voltage of the radiation generating unit 12 in the second imaging is displayed. It is displayed in the setting / display field 76 in the screen. Accordingly, the user can recognize the current imaging conditions (the tube voltage of the radiation generating unit 12 and the imaging time interval in the first and second imaging) by referring to the displayed imaging condition setting screen. it can.

  In step 108, it is determined whether or not the user has instructed the start of shooting. If the determination is negative, the process proceeds to step 110, and it is determined whether or not the user has instructed to change the tube voltage in the first or second imaging. If this determination is also negative, the process proceeds to step 112, and it is determined whether or not the user has instructed to change the shooting time interval. If this determination is also negative, the process returns to step 108, and steps 108 to 112 are repeated until any determination is affirmed.

  A user who has recognized the current imaging conditions by referring to the displayed imaging condition setting screen needs to change the tube voltage of the radiation generator 12 based on the physique of the subject 18 (photographed person), for example. If it is determined that there is, the operation panel 28 is operated by the user, and is displayed in the tube voltage or the setting / display field 76 in the first shooting displayed in the setting / display field 72. The tube voltage in the second shooting is changed. When the above operation is performed by the user, it is determined that the user has instructed to change the tube voltage, the determination in step 110 is affirmed, the process proceeds to step 114, and is read from the imaging condition information DB and stored in the memory. Among the shooting condition information, the tube voltage at the first or second shooting instructed by the user to be changed is changed and set.

  In the next step 116, it is determined whether or not the difference between the tube voltage in the first shooting and the tube voltage in the second shooting has become smaller with the change setting of the tube voltage in step 114. As shown in Table 1 above, in the present embodiment, the tube voltage in the first imaging is made smaller than the tube voltage in the second imaging regardless of the imaging region (the dose of radiation in each imaging). In step 116, the tube voltage in the first imaging is increased by the user, or the tube voltage in the second imaging is determined by the user. Affirmed if decreased by the user.

  When the determination in step 116 is affirmed, the change of the tube voltage by the user is a change in which the difference between the tube voltage in the first shooting and the tube voltage in the second shooting is reduced, and in the energy subtraction image Since there is a risk of image quality deterioration such as a decrease in contrast, the process proceeds to step 118, and the tube voltage not changed in step 114 is set to 1 among the tube voltage in the first shooting and the tube voltage in the second shooting. The difference between the tube voltage at the second imaging and the tube voltage at the second imaging is changed to be equal to the difference between the tube voltages represented by the imaging condition information stored in the imaging condition information DB (for example, If the tube voltage in the shooting is increased by the user, the tube voltage in the second shooting is also increased by the same amount, and if the tube voltage in the second shooting is decreased by the user, the first shooting Tube voltage at Decrease amount), the flow returns to step 108.

  Thereby, it is possible to prevent the image quality deterioration such as the contrast reduction in the energy subtraction image from occurring due to the change of the tube voltage by the user. In addition, when the user changes one of the tube voltage in the first shooting and the tube voltage in the second shooting, the other is automatically changed when the difference from the tube voltage becomes small. When changing the voltage, the user does not need to be aware of a decrease in contrast in the energy subtraction image, and the user can easily change the tube voltage.

  If the determination in step 116 is negative (the tube voltage in the first shooting is decreased by the user or the tube voltage in the second shooting is increased by the user), the user The change of the tube voltage due to the change is a change in which the difference between the tube voltage in the first shooting and the tube voltage in the second shooting becomes large, and it can be determined that there is no reduction in contrast in the energy subtraction image. The process returns to step 108 without performing any processing. Instead of this, as in the previous step 118, the tube voltage that has not been changed in step 114 of the tube voltage in the first shooting and the tube voltage in the second shooting is changed in the first shooting. The difference between the tube voltage and the tube voltage at the second imaging may be changed to be equal to the difference between the tube voltages represented by the imaging condition information stored in the imaging condition information DB (for example, at the first imaging). When the tube voltage is reduced by the user, the tube voltage at the second shooting is also decreased by the same amount, and when the tube voltage at the second shooting is increased by the user, Increase the tube voltage by the same amount).

  In addition, when the user who has recognized the current shooting condition needs to change the shooting time interval by referring to the displayed shooting condition setting screen, the user operates the operation panel 28. The shooting time interval displayed in the setting / display field 74 is changed. When the above operation is performed by the user, it is determined that the user has instructed to change the shooting time interval, the determination in step 112 is affirmed, the process proceeds to step 120, the memory is read from the shooting condition information DB, and is read. After changing the shooting time interval in the shooting condition information held in the above, the process returns to step 108.

  As described above, in the present embodiment, the user can also change the shooting time interval. Therefore, for example, when shooting the chest of the subject 18 (photographed person), the cardiac cycle of the subject is measured and the measured heart rate is measured. The user can change and set the shooting time interval so as to approach the cycle. In this case, motion artifacts in the energy subtraction image can be reduced.

  As described above, confirm that the shooting conditions displayed in the shooting condition setting screen are appropriate by instructing to change the shooting conditions (tube voltage and shooting time interval) as necessary. The user who has operated the operation panel 28 selects the button 78 in the screen. If the button 78 is selected, it is determined that the user has instructed the start of shooting, the determination in step 108 is affirmed, and the routine proceeds to step 122. In step 122, information indicating whether or not image quality correction processing is performed in the first shooting is referred to among the current shooting condition information stored in the memory, and whether or not the image quality correction processing is performed is determined based on the information. The processing unit 58 is instructed. In the next step 124, the radiation generation control unit 20 is notified of the imaging conditions (tube voltage) in the first imaging set in the current imaging condition information stored in the memory, and the execution of imaging is instructed. To do.

  As a result, the radiation generation control unit 20 causes the radiation generation unit 12 to generate radiation while controlling the tube voltage at the time of radiation generation by the radiation generation unit 12 to match the tube voltage notified from the control unit 24. The radiation generated by the radiation generation unit 12 is irradiated to an imaging part set by the user among the subjects 18 located at the imaging position, passes through the imaging part and is incident on the radiation detection panel 14, and the radiation detection panel. The charge is accumulated in the storage capacitor 36 of each of the 14 pixel units 40 as charges. When the generation of radiation by the radiation generation unit 12 is completed, the image information (signal charge) is read from the radiation detection panel 14 (the storage capacitor 36 of each pixel unit 40 thereof) by the signal detection correction unit 22. If the execution of image quality correction processing is instructed to the image quality correction processing unit 58 in the previous step 122, the image quality correction processing unit 58 performs image quality in parallel with reading of image information from the radiation detection panel 14. Correction processing is also performed.

  In the next step 126, image data is acquired from the signal detection correction unit 22, and the acquired image data is stored in the storage unit 24A or the like as image data obtained by the first shooting. In Step 128, whether or not a time corresponding to the imaging time interval set in the current imaging condition information stored in the memory has elapsed since the radiation generation unit 12 generated radiation in the first imaging. Step 128 is repeated until the determination is affirmative. If the determination in step 128 is affirmed, the process proceeds to step 130, and information indicating whether or not image quality correction processing is performed in the second shooting is referred to from the current shooting condition information stored in the memory, and based on the information. The image quality correction processing unit 58 is instructed whether or not to perform image quality correction processing. In step 132, the radiation generation control unit 20 is notified of the imaging conditions (tube voltage) in the second imaging set in the current imaging condition information held in the memory, and the execution of imaging is instructed.

  Thereby, the radiation generation control unit 20 causes the radiation generation unit 12 to generate radiation again while controlling the tube voltage at the time of radiation generation by the radiation generation unit 12 to match the tube voltage notified from the control unit 24. . The radiation generated by the radiation generating unit 12 is irradiated to the same imaging part as that of the first imaging among the subject 18 located at the imaging position, passes through the imaging part, and enters the radiation detection panel 14 to detect radiation. The charges are stored in the storage capacitor 36 of each pixel unit 40 of the panel 14 as charges. When the generation of radiation by the radiation generation unit 12 is completed, the image information (signal charge) is read from the radiation detection panel 14 (the storage capacitor 36 of each pixel unit 40 thereof) by the signal detection correction unit 22. If the execution of image quality correction processing is instructed to the image quality correction processing unit 58 in the previous step 130, the image quality correction processing unit 58 performs image quality in parallel with reading of image information from the radiation detection panel 14. Correction processing is also performed.

  In the next step 134, image data is acquired from the signal detection correction unit 22, and the acquired image data is stored in the storage unit 24A or the like as image data obtained by the second shooting. In step 136, the difference is calculated by assigning different predetermined weights to the image data obtained by the first shooting and the image data obtained by the second shooting stored in the storage unit 24A. Then, an energy subtraction image is generated, and the generated energy subtraction image is displayed on the display 26. In step 138, based on information defining the diagnostic image among the current imaging condition information held in the memory, the image obtained by the first imaging and the image obtained by the second imaging are included. An appropriate image for diagnosis is determined, the determined image is displayed on the display 26 as a diagnostic image, and the process ends. In steps 136 and 138, an image may be displayed when the user instructs display on the display 26.

  The imaging condition setting screen and flow are not limited to the above, and the imaging region may be determined in advance, and only the tube voltage and the imaging time interval may be set.

  Among the imaging parts shown in Table 1, since the heart or the like that works by the involuntary muscle enters the imaging range, the degree of the influence of the imaging time interval on the motion artifact is large. Moreover, in the radiography of the chest, an image photographed with radiation having a higher tube voltage among a plurality of images obtained by a plurality of photographings with different radiation doses and tube voltages is suitable as a diagnostic image. Based on the above, in this embodiment, as shown in Table 1, for the chest, the image obtained by the second imaging is used as a diagnostic image, and the image obtained by the first imaging is not used for diagnosis or the like. The image quality correction processing in the first shooting is set to “None”, the radiation dose in the first shooting is relatively small, and the image quality correction processing in the first shooting is set to “None”. Therefore, as shown in Table 1, the imaging time interval when imaging the chest is significantly smaller than other imaging regions. Thereby, the motion artifact of an energy subtraction image can be reduced. In addition, since the image quality correction process in the second shooting is set to “present”, a high-quality image can be obtained as a diagnostic image.

  On the other hand, among the imaging parts shown in Table 1, the imaging parts other than the chest (lumbar vertebrae, limb bones, breasts, etc.) do not fall within the imaging range of the organs that work due to involuntary muscles, so the imaging time interval affects the motion artifact. The degree of influence is small. Further, in radiography of these imaging regions, images taken with radiation at a lower tube voltage are suitable as diagnostic images among a plurality of images obtained by multiple imagings with different radiation doses and tube voltages. Yes. Based on the above, in the present embodiment, as shown in Table 1, for each imaging region other than the chest, an image obtained by the first imaging is used as a diagnostic image, and image quality correction processing in the first imaging is “present” As shown in Table 1, based on the fact that the radiation dose in the first imaging is relatively large and the image quality correction processing in the first imaging is set to “present”. In addition, the shooting time interval is significantly larger than that of the chest. Thereby, a high quality image is obtained as a diagnostic image. In addition, each imaging region other than the chest has a small degree of influence of the imaging time interval on motion artifacts, such as holding the imaging region from the outside or requesting the subject not to move the imaging region, etc. By another means, motion artifacts in the energy subtraction image can be reduced.

  In the above, the embodiment in which the present invention is applied to the generation of the energy subtraction image has been described. However, the present invention is not limited to this, and the dose of radiation and the tube voltage in a plurality of imaging operations are fixed, and frame advance is performed. The present invention can also be applied when shooting such moving images (semi-moving images).

  In video shooting, there is a demand to analyze and analyze a series of movements. Also in this motion analysis, the necessary imaging interval differs depending on the imaging region. For example, the chest can be used for diagnosis by observing the motion of the lungs due to breathing with a moving image. Since there is a high demand to see the movement of the lung in detail with images of a short time interval, it is conceivable to shorten the imaging time interval. On the other hand, for lumbar vertebrae and limb bones, it may be possible to determine whether the movement of joints and bones is normal by moving images. These movements do not need to be observed at such a short time interval, and can be controlled by the patient more easily than breathing, so the imaging time interval may be long. In addition, since the chest is high tube voltage imaging, it is easy to shorten the imaging time. Therefore, an image suitable for each part can be provided by shortening the imaging time interval in the chest and increasing the imaging time interval in the lumbar vertebrae and limb bones.

  In the above description, the radiation detection panel 14 provided with the photoelectric conversion layer that directly converts the irradiated radiation into electric charges has been described as an example of the image detection unit according to the present invention. However, the present invention is not limited to this. The photoelectric conversion unit that converts the irradiated radiation into electric charge in the image detection means once converts the irradiated radiation into electromagnetic waves (eg, visible light), and then converts the converted electromagnetic waves into electric charges (indirect conversion) System). In the above description, the configuration in which the photoelectric conversion layer is formed on the TFT active matrix substrate 34 has been described. However, the photoelectric conversion unit includes a substrate on which a plurality of pixel units each including a storage capacitor and a switching unit are arranged. It may be a separate body.

  In the above description, the radiation detection panel 14 having a configuration in which a large number of pixel portions 40 (TFTs 38 and storage capacitors 36) are arranged in a matrix (two-dimensionally) has been described as an example. However, the present invention is not limited to this. The radiation detection panel may have a configuration in which a plurality of pixel portions are arranged in a row (one-dimensionally).

  In the above description, X-rays are described as an example of radiation generated by the radiation generating means according to the present invention. However, the present invention is not limited to this, and the charge is converted into charges by the image detecting means and stored in the storage capacitor. May be another radiation such as an electron beam or an α ray.

It is a block diagram which shows schematic structure of the radiographic imaging system which concerns on this embodiment. It is a schematic block diagram of a radiation detection panel and a signal detection correction | amendment part. It is a flowchart which shows the content of the continuous imaging process performed by the control part. It is an image figure which shows an example of an imaging condition setting screen.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Radiation imaging system 12 Radiation generation part 14 Radiation detection panel 16 Control apparatus 20 Radiation generation control part 22 Signal detection correction part 24A Storage part 24 Control part 58 Image quality correction process part

Claims (12)

Radiation generating means for generating radiation;
Image detecting means for detecting, as an image, radiation generated by the radiation generating means and transmitted through the subject;
Control means for changing the shooting time interval in the plurality of shootings according to the set shooting part of the subject when shooting the same subject a plurality of times continuously,
A radiographic imaging apparatus including:   The control unit controls the radiation generating unit so that the radiation dose in each imaging monotonously increases when imaging the same subject a plurality of times continuously, regardless of the set imaging region of the subject. The radiographic imaging apparatus according to claim 1.   The control means controls the radiation generating means so that the tube voltage of the radiation in each imaging monotonously increases when imaging the same subject a plurality of times continuously, regardless of the set imaging region of the subject. The radiographic image capturing apparatus according to claim 1, wherein:   The control means determines whether to output an image obtained by the first imaging as a diagnostic image or to output an image obtained by the second imaging as a diagnostic image as a set imaging region of the subject. The radiographic image capturing apparatus according to claim 3, wherein the radiographic image capturing apparatus is switched according to the selection. Further comprising storage means for storing the set value of the shooting time interval for multiple shootings for each shooting part of the subject,
2. The radiographic image capturing apparatus according to claim 1, wherein the control unit reads out a setting value of an imaging time interval corresponding to the set imaging region of the subject from the storage unit and uses it for controlling the imaging time interval. .   When the change of the shooting time interval is instructed via the instruction unit, the control unit changes the setting value of the shooting time interval read from the storage unit according to the instruction, and takes the changed set value. 6. The radiographic image capturing apparatus according to claim 5, wherein the radiographic image capturing apparatus is used for controlling a time interval. In the storage means, parameters that define the imaging conditions in each imaging among a plurality of imaging are also stored for each imaging region of the subject,
6. The control unit according to claim 5, wherein the control unit reads out the parameter corresponding to the set imaging region of the subject from the storage unit, and uses the parameter to control imaging conditions in each imaging of a plurality of imagings. The radiographic imaging apparatus as described.   The control means is configured to control the specific times specified by the parameters read from the storage means when an instruction for changing photographing conditions in a specific number of times of photographing is designated via the instruction means. The shooting conditions for shooting are changed, and the shooting conditions for shooting other than the specific times among the plurality of times of shooting are also changed according to the changed shooting conditions for the specific times of shooting. The radiographic imaging device according to claim 7. The imaging conditions include a tube voltage in the radiation generating means,
When the tube voltage at the specific time is changed, the control means does not cause the difference in the tube voltage in each photographing to be smaller than the difference in the tube voltage defined by the parameter read from the storage means. The radiographic image capturing apparatus according to claim 8, wherein the tube voltage in the imaging other than the specific time is also changed. Further comprising an acquisition / correction means for performing an image quality correction process for improving the image quality of the acquired image while acquiring the image detected by the image detection means from the image detection means during each shooting.
The radiographic image capturing apparatus according to claim 1, wherein the control unit switches whether to perform the image quality correction processing by the acquisition / correction unit according to the set imaging region of the subject. Further comprising an acquisition / correction means for performing an image quality correction process for improving the image quality of the acquired image while acquiring the image detected by the image detection means from the image detection means during each shooting.
The radiographic imaging according to claim 1, wherein the control unit switches whether or not the image quality correction processing is performed by the acquisition / correction unit in units of each imaging among a plurality of imaging. apparatus. The image detecting unit includes a plurality of pixel units each including a switching unit that is turned on / off in response to an on / off signal supplied via the first signal wiring and a holding unit that holds a signal charge corresponding to the irradiation radiation dose. Provided,
The acquisition / correction means acquires, as the image quality correction processing, a signal output from the second signal wiring when the switching means is on and off, and outputs the output signal from the on-time to the off-time output signal. 12. The radiographic imaging according to claim 10, wherein at least one of leak correction processing for reducing the frequency and electrical noise suppression processing for averaging the output signal by converting the output signal into digital data a plurality of times is performed. apparatus.

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